The invention concerns image data processing. More particularly, the invention pertains to high speed, post-processing of image data to adaptively effect gray level tone scale adjustment of document imagery at an image-based data entry work station. Still more specifically, the invention is directed to a method of generating a pixel remapping formation to effect the gray level adjustment.
Financial documents, such as checks or drafts, usually contain a magnetic ink character recognition (MICR) code line which is typically read by a sorter and which automatically sorts these documents into a plurality of bins. Prior to sorting, in current practice, these documents are presented to banking personnel who physically handle the documents and mechanically enter, in MICR form, the dollar amount associated therewith upon each document by the use of specialized amount entry equipment. Additionally, these individuals physically correct incorrectly read MICR data associated with each of the sorted documents.
These prior techniques of utilizing banking personnel to process financial documents have proven relatively costly and inefficient, in that many of these documents have been lost or destroyed during their physical handling, and the speed associated with the processing of the documents is limited to that associated with the processing capabilities of the banking personnel and the mechanical amount entry equipment they use.
To address these problems, document imaging systems have been introduced to eliminate much of the previously required physical handling of the documents themselves. In such known systems, functions such as image data element normalization, background suppression, scaling and document height detection are performed as preprocessing functions prior to compression of the document image data for storage or transmission to a data decompressor.
Previous approaches for effecting background suppression in document image processing systems to yield higher contrast images for data entry operators are complex. Additionally, for imaging systems to be associated with archival storage systems, the original image data cannot be discarded in a suppression technique, but must be maintained for archival integrity. Therefore, there is a need for an efficient, relatively non-complex approach to gray level tone scale adjustment, such as thresholding image pixel data, in order to yield picture-like representations of the image at the workstation which feature increased contrast of written and printed text for viewing by a data entry operator. Such gray level tone scale adjustment also finds use in printing and facsimile transmission applications.